1. Field of the Invention
The present invention relates to novel chemical compounds and, more specifically, it relates to novel sulfam(na)phthaleins useful as optical filter agents and filter agent precursors in photographic processes for protecting an exposed photosensitive material from post-exposure fogging during development in the presence of ambient light.
2. Description of the Prior Art
A number of diffusion transfer processes for producing photographic images in both black-and-white and in color have been proposed. Of particular interest are diffusion transfer processes wherein the image-receiving layer carrying the transfer image is not separated from the developed photosensitive layer(s) after processing but both components are retained together as a permanent laminate. Included as part of the laminate is a layer of light-reflecting material, preferably titanium dioxide, positioned between the image-carrying layer and the developed photosensitive layer(s). The light-reflecting layer separating the image-carrying and photosensitive components provides a white background for the transfer image and masks the developed photosensitive layer(s). In addition to these layers, the laminate usually includes dimensionally stable outer layers or supports, at least one of which is transparent so that the resulting transfer image may be viewed by reflection against the background provided by the light-reflecting layer. Diffusion transfer processes for forming images viewable without separation of the photosensitive and image-receiving components and integral negative-positive film units useful in such processes, i.e., film units wherein the negative or the photosensitive component and the positive or image-receiving component are retained as a permanent laminate after processing are described in U.S. Pat. Nos. 3,415,644, 3,415,645 and 3,415,646 issued Dec. 10, 1968 to Edwin H. Land, U.S. Pat. Nos. 3,573,043 and 3,573,044 issued Mar. 30, 1971 to Edwin H. Land and U.S. Pat. Nos. 3,594,164 and 3,594,165 issued July 20, 1971 to Howard G. Rogers.
U.S. Pat. No. 3,647,437 issued Mar. 7, 1972 to Edwin H. Land also is concerned with diffusion transfer processes wherein the resulting photograph comprises the developed photosensitive layer(s) retained with the image-receiving layer as part of a permanent laminate. In the processes disclosed in this patent, a photographic film unit comprising a photosensitive element is developed in ambient light but further undesired exposure during processing is prevented by a light-absorbing material or optical filter agent which is retained in the processed film unit. In a preferred embodiment, the optical filter agent is a pH-sensitive dye, i.e., a dye possessing spectral absorption characteristics that are reversibly alterable in response to changes in environmental pH and particularly, a pH-sensitive dye having a colored or light-absorbing form above a given alkaline pH and a colorless or non-light-absorbing form below said pH. Though the pH-sensitive dye is usually included in the processing composition, it may be initially positioned in the film unit, for example, in a layer over the photosensitive element provided it is in its colorless form if photoexposure is to be effected through that layer. Upon application of an alkaline processing composition, the pH-sensitive dye is converted to its colored form, and after the desired processing time, it is converted back to its colorless form by reducing the environmental pH, e.g., by including an acid-reacting layer as part of the film unit. Examples of pH-sensitive dyes found particularly useful as optical filter agents are the phthalein and naphthalein dyes disclosed in U.S. Pat. No. 3,702,244 issued Nov. 7, 1972 to Stanley M. Bloom, Alan L. Borror, Paul S. Huyffer and Paul T. MacGregor and in U.S. Pat. No. 3,702,245 issued Nov. 7, 1972 to Myron S. Simon and David P. Waller and also the 9-pyridyl fluorene dyes disclosed in U.S. Pat. No. 3,726,675 issued Apr. 10, 1973 to Alan L. Borror.
Copending U.S. patent application Ser. No. 836,006, now U.S. Pat. No. 4,139,381 of Stanley M. Bloom, Alan L. Borror and James W. Foley filed concurrently herewith is concerned with the use of a different class of optical filter agents in integral negative-positive film units which are generated from substantially colorless filter agent precursor compounds and are capable of being discharged independently of a change in pH. The colorless filter agent precursor is initially disposed in a layer of the film unit, for example, in a layer coated over the photosensitive element, and subsequent to imagewise exposure of the photosensitive element, the colored optical filter agent is generated by contacting the colorless precursor with base, e.g., an aqueous alkaline processing composition. After remaining in contact with said base for a given time, the colored optical filter agent is discharged by forming a new compound which is substantially colorless and which is different from and non-reversible by a pH change to either said optical filter agent or said precursor. Compounds, i.e., optical filter agent precursors found useful for generating a colored optical filter agent above a given alkaline pH which, in turn, generates a colorless product above said given pH are those possessing (i) an ionizable proton removed in base to generate a chromophore and (ii) a moiety that undergoes an irreversible cleavage reaction with base with resultant destruction of said chromophore to yield a substantially colorless product.
Dutt, J. Chem. Soc., 121, p. 2389 (1922) reported the condensation of saccharin with aromatic amines and phenols in the presence of concentrated sulfuric acid and also in the presence of fused zinc chloride. The resulting condensation products with saccharin were named "sulfamphthaleins" by analogy to "phthaleins" and "sulfonephthaleins". Though the structure 3,3-di(4'-hydroxyphenyl)-2,3-dihydrobenz[d]isothiazole-1,1-dioxide (named "phenolsulfamphthalein") was assigned to the condensation product obtained with saccharin and phenol, it has been determined that the compound corresponding to the proposed structure has properties different from those reported, for example, colorless rather than pink in alkali. Also, it has been found that the compound corresponding to the structure given could not be synthesized by repeating the procedures reported by Dutt.
The present invention is directed to novel sulfam(na)phthaleins which find utility in the above-described photographic products and processes as colorless precursors for providing colored optical filter agents for protecting an imagewise exposed photosensitive element from further undesired exposure during processing in ambient light.